Novel method for the homogenous loading of solid particles in a chamber

ABSTRACT

The invention concerns a method whereby the chamber ( 1 ) is filled at least partly with a liquid ( 2 ), and the flux of particles ( 3 ) introduced into the chamber ( 1 ) is divided, then homogeneously distributed in a gas phase ( 4 ) above the surface ( 5 ) of the liquid, wherein the particles descend by gravity, to be deposited while forming a fixed bed.

[0001] This invention relates to a new process for the homogenousloading of solid particles into a chamber.

[0002] This process relates more specifically to the filling of chemicalor electrochemical, oil or petrochemical type reactors with solidparticles in a divided state, that may be in the form of beads, grains,cylinders, pellets, sticks, or other shapes but all relatively small insize.

[0003] These particles may namely be molecular sieves or solid grains ofcatalyst, usually extruded, either irregular in shape or in the form ofbeads, or mono- or multilobar, whose dimensions vary, as applicable,from a few tenths of a millimeter to a few centimeters.

[0004] It is to this application in particular that we will refer in theremainder of this description, but the process as set forth in theinvention naturally applies to the loading of any other type of particlein a chamber.

[0005] It is known that a fixed bed reactor has a better reaction yieldwhen its catalytic mass is loaded in the most homogenous way possible.This homogeneity, which, for reasons of simplicity and efficiency, mustbe obtained during the loading phase of the catalyst, makes it possibleto guarantee a uniform and constant contact between the various catalystgrains and the liquid reaction medium, without creating preferred pathsfor the latter.

[0006] Today's most commonly used loading methods consist in loading thereactor's fixed bed using a flexible tube, still called “sleeve” or“sock”, from the term “sock loading”, or using buckets filled withcatalyst, whose contents are successively poured into the reactorthrough the hole of the upper part of the chamber to be loaded (called“man hole” or “filling hole”).

[0007] These methods lead to charges loads done in a point-to-pointmanner in the reactor, usually favoring the creation of slopes and taluson the surface of the bed being loaded. The various directions of thegrains and the segregation of the heavier ones as they roll along saidslopes or talus naturally lead to heterogeneities that are harmful tothe proper further operation of the reactor. Indeed, preferred paths,followed by the liquid reaction phase, then become apparent in thecatalytic bed, because of the random presence of significant spacesbetween the catalyst grains thus loaded. Consequently, the contact ofthe liquid with the various catalyst grains, as well as the duration ofsaid contact, decrease and lead to an incomplete chemical reaction thatmay lead to an obvious deactivation of the overall catalytic mass.

[0008] We have also known for some time that, to correct this problemand therefore increase the homogeneity of a catalytic bed that is to beloaded, we can use a loading process that is no longer point-to-pointbut rather distributed over the entire section of the chamber to beloaded, similar to rain. This distribution of solid particles using arainlike effect is usually carried out using units placed above acatalyst grain feeding device, and comprised, for example, of a rotatingcone, for a distribution of particles using a centrifuge effect, asdescribed in the US patent A-3 804 273, or using static elements, ontowhich the catalyst grains fall and in whose direction air is sometimesblown sideways, as outlined in the US patent A-4 051 019. Other types ofequipment have also been suggested in order to obtain an overallhomogonous distribution over the entire surface of the bed to be loaded,for example in FR-A-2 319 427 and, more recently in DE-A1-198 35 699.

[0009] The applicant has patented a process and a device for the uniformdistribution of a solid in divided form into a chamber, which are namelythe object of EP-A-007 854 and EP-A-1 16 246 as well as EP-A-769 462.

[0010] Unfortunately, if all these loading processes, which are groupedunder the name “dense loadings” have a tendency to increase thehomogeneity of the catalytic mass, they also favor in considerableproportions a gain in the density of the load itself. This gain indensity may be greater than 10%, even 20%, when a method of denseloading is used instead of the method called “the sleeve”.

[0011] The result is inevitably that the spaces between the catalystgrains, in which the reactor's reaction fluid must circulate, aresmaller, which increases the difference in pressure between the inputand the output of the load to be treated in the reactor, where saiddifference is called AP or loss of load of the reactor.

[0012] However, it turns out that in some cases and for some processesthe industrial entrepreneur need only benefit from the improvedhomogeneity of the catalytic bed so obtained, without being subjected tothe increase in the loss of load of the reactor.

[0013] In pursuing her/his work in this field, the applicant establishedthat it is possible to obtain this result by distributing the particlesin the chamber to be loaded over a liquid contained in said chamber andcompatible with said particles, where the bed of particles is thusformed within said liquid.

[0014] The applicant has indeed noticed that, during traditional typedense loadings, meaning in a chamber that only contains a gaseous phase,the increase in the load density is most likely linked to the free fallvelocity of the grains, and therefore to their impact energy when theyarrive on the bed being formed, associated with a preferred angle ofsaid grains in the catalytic bed. Therefore it appears that by using aliquid as an intermediary to reduce said fall velocity, it is possibleto resolve in a simple way, both the problem of the homogenousdistribution of the grains and that of the increase in density.

[0015] Therefore, the object of this invention is a process forhomogenous loading of solid particles into a chamber, characterized inthat said chamber is filled, at least in part, with a liquid, and inthat the flow of particles introduced in the chamber is divided, thendistributed in a homogenous manner in a gaseous phase over the surfaceof said liquid, within which the particles move downward by means ofgravity and come to settle while forming a fixed bed.

[0016] A first advantage of the process that is the object of theinvention is therefore to obtain good homogeneity of the formed bed,without increasing the density of the load. Indeed, in limiting thespeed at which the grains fall into the liquid, it is possible to limitthe energy of their impact, and thus favor the creation of sufficientlysignificant voids between the grains and, in the case of catalystgrains, a better contact and freer passage of the reaction liquidbetween said grains, without creating preferred paths, thus reducing bysuch the loss of load of the reactor.

[0017] A second advantage as set forth in the invention is thepossibility of loading grains, namely catalysts, with a more fragilemechanical strength, for example extrudates in the form of cylinderswhose length is several times greater than their diameter, for example alength that is greater than 5 millimeters or more, for a diameter ofapproximately 1 millimeters Indeed, these extruded grains have atendency to break when the dense loaded grains under gaseous atmosphereknock against each other, during their impact upon arriving on thecatalytic bed. Indeed, the liquid phase used in the process as set forthin the invention limits said striking energy on the bed, which is thecause of grain breakage while also decreasing the phenomenon ofattrition between the latter, thus reducing the quantity of catalystfines or dust formed during the loading of the catalyst.

[0018] A third advantage of the process as set forth in the invention islinked to the decrease of the gaseous volume in the reactor due to thepresence of the liquid in a quantity that is more or less significant.Said decrease may be a favorable element for implementing the loadingprocess in the case where the particles, namely the catalyst, show achemical reactivity with the loading gas, for example the air's oxygen.It can also be an important economic factor, because of the lesserquantity of gas that needs to be introduced into the reactor, when itinvolves a rare or inert gas, such as for example argon or nitrogen.

[0019] All types of liquids as well as their mixtures may therefore beused in implementing the process that is the object of the invention,provided that the catalyst grains that arrive at the upper level of theliquid may freely pass through said liquid up to the surface of thecatalytic bed.

[0020] The man of the art will therefore choose a liquid or a mixture ofliquids that are physically and chemically compatible with each other,as well as with the nature of the particles to be loaded, whoseconstitution and physico-chemical characteristics, such as for exampledensity and viscosity, vary based on the parameters and precautionssurrounding the loading. In the case of a chemical reactor and catalystparticles, the liquid being used may be the reaction liquid, ahydrocarbon such as an oil, water, or any other type of aqueous product.A liquid that evaporates rapidly, for example an alcohol, may also beused so as to evaporate at the end of the loading.

[0021] The distance needed for a solid particle, such as a grain ofcatalyst used to load reactors, to reach its speed limit in a liquid isin the range of a few centimeters, and it is therefore not necessary tohave a large quantity of liquid over the surface of the catalytic bed.However, the height of the liquid in the reactor varies based on thequantity of loaded catalyst, this height must constantly be maintainedgreater than that of the bed throughout the loading, to make it possibleto limit the fall velocity of the grains as proposed in this invention.The man of the art will calculate the quantity of liquid directlynecessary for the loading, or will use known means to adjust said heightbased on the quantities of loaded catalyst. Preferably, the height ofthe liquid above the surface of the catalytic bad of particles will begreater than 10 cm.

[0022] The loading process that is the object of this invention makes itpossible to use various types of gases in chemical reactors whose naturemay vary based on the reactivity of the catalysts with said gases.Namely, the ambient air is generally used to load reactors, for examplehydrotreatment reactors in the oil industry, and said air could be driedout or dehydrated to adapt it to the specific conditions needed to loadcertain types of catalysts.

[0023] Neutral or inert gases, such as for example argon or nitrogen,can be used to load specific catalysts intended for specific processes,such as for example isomerization catalysts for light gasolines in anoil refinery.

[0024] All methods of dense loading implemented in the traditional way,meaning whose grain distribution device allows for a homogenousdistribution of the grains all along the transversal section of thereactor or the chamber to be loaded, over the surface of a liquid, arelikely to be used in accordance with the invention. In particular whenthe reactor must be loaded up to its upper part, one should use devicesthat can create a homogenous rain in the small gaseous space availableover the liquid at the end of the loading. Advantageously, rotarydevices that can spread out under the effect of the speed of rotation inthe highest part of the reactor over at least half the transversalsection of the latter will be put in place at the man hole or fillinghole level arranged under a catalyst grain feeding sieve.

[0025] Preferably, we will use the device described in EP-A-769 462 orits equivalents. Indeed, this device includes a mobile axis, on whichflexible deflector elements, each shaped like a vertical strap inresting position, are arranged at various levels and articulated so asto be able to lift up under the effect of the centrifugal force. Saidflexible deflectors, which may for example be made of a rubbery matterand be animated with a slow rotation speed, generally less than 200rotations per minute and preferably less than 150 rotations per minute,make it possible to limit the breaking of the catalyst grains that knocktogether when falling on the deflectors and the attrition phenomena thatlead to the creation of catalyst fines. For some uses, the device may beput in place in a fixed manner level with the man hole, or lowered intothe reactor and then be brought back up at the same time as thecatalytic bed during the loading. Of course, other grain distributiondevices can also be used such as those described above, whosedistribution device is comprised of a rigid matter as described in EP 0470 142 or FR-A-2 721 900.

[0026] Various types of solid particles can be loaded using the processthat is the object of this invention such as beads, grains, cylinders,pellets, sticks, mono or multilobar shapes, or any other shapes whosevarious dimensions go from a few tenths of millimeters to a fewcentimeters. It could be catalyst grains, molecular sieve grains,contact mass grains for the needs of the chemical, oil or petrochemicalindustries. Other types of solid particles, with the dimensionsindicated above and requiring a homogenous loading into a chamber, canof course be used.

[0027] The process as set forth in the invention allows for the loadingof particles with a reactivity to the gaseous fluid, because of theirshort residence time in the latter, as the particles quickly end up inthe liquid medium, which can be chosen to be chemically compatible withthe nature of the particles. Liquid impregnations can also be made onsaid catalyst grains, prior to being loaded into the reactor, where saidliquid can be of the same nature as that contained in the reactor, orsimply chemically and physically compatible with it. Arrangements knownto the man of the art, such as for example liquid flows in the form ofsprays are then necessary upstream from the distribution, to break thegrain aggregates and carry them through the distribution device using arain effect.

[0028] The attached drawings represent a non restrictive manner ofimplementing the process as set forth in the invention and results ofcomparative examples that will be described hereafter.

[0029] About the drawings:

[0030]FIG. 1 is a schematic view of a chamber during loading using theprocess as set forth in the invention;

[0031]FIG. 2 is a schematic view of a chamber prior to loading;

[0032]FIG. 3 is a schematic view of the same chamber after loading;

[0033]FIGS. 4, 5 and 6 are representations of photos of the surface ofthe catalytic bed after successive loadings of the same catalyst grains,using the process called “sleeve” under gaseous atmosphere, after aloading under the same conditions as previously mentioned, but replacingthe sleeve with a dense loading device and lastly following a loading inliquid, as set forth in the invention respectively.

[0034]FIG. 1 represents a chamber 1, for example a chemical reactor,whose diameter and height may reach several meters, in which thecatalytic bed 6, whose mass is supported in the reactor 1 by inert beads7, is being loaded.

[0035] As set forth in the invention, a liquid 2, for example water, isarranged over said bed. Over said liquid, the gaseous phase can becomprised of various gases, namely air. The catalyst grains arecontinuously introduced into the upper part of the reactor, for examplethrough a feeding sieve 3, then fall onto a distribution device so as tolater obtain a homogenous distribution of said grains in the reactor 1.

[0036] The device represented and used in a preferred way, commerciallycalled “Densicat”, is described in detail in EP-A-0 769 462. Said deviceis comprised of rubber flexible deflectors, integral with several levelsof a mobile axis, whose rotation speed is variable, to adjust thequality of the loading. The deflectors move further and further awayfrom the mobile axis as the rotation speed of the latter increases,where said speed can reach more than a hundred rotations per minute. Thegrains of catalyst, after falling onto said rotation deflectors, aredispersed like rain in the gaseous phase over the entire transversalsection of the reactor, above the surface of the liquid 5. The fallvelocity of the grains passing through the liquid 2 is then slowed down,thus making it possible to reduce the grains' striking energy when thelatter come into contact with the surface of the catalytic bed 6. Thanksto this decrease in energy, the grains can settle more softly and in amore homogenous manner on the catalytic bed, without grouping together,thus creating even spaces between them, reducing by as much the densityof the loading.

[0037] It is important to make sure that, during the loading, the heightof the liquid over the catalytic bed remains at least at its minimumlevel, and it will be adjusted by any means known if necessary.

[0038] The liquid phase introduced into the reactor before the loadingcan have any height, but is should preferably be greater than tencentimeters, which corresponds to the minimum level 8 indicated in FIG.2.

[0039] At the end of the loading, the liquid reaches its highest level9, indicated in FIG. 3. The previously described device comprised ofdeflectors makes it possible, through its small overall dimensions, tobe operational even if the maximum level of liquid 9 is very close tothe upper extremity of the reactor.

[0040] In FIG. 4, we see the aspect of the catalytic bed surface,following loading with a feeding sleeve, which makes it possible todistribute the catalyst grains over the surface of the bed, at best in apoint-to-point manner and using human means. The spaces between thegrains are distributed randomly and the grains are not packed down,offering numerous and important preferred paths for the reaction liquid,that lead to an incomplete chemical reaction. The loading is nothomogenous and not dense.

[0041] On the other hand, in FIG. 5, the catalyst grains are very muchgrouped together and take up the maximum available space therefore thevoids between the particles are very small. The dense loading carriedout for this test made it possible to load the reactor in a homogenousand dense manner, meaning with a maximum of catalyst grains in thereaction liquid, but leaving very few spaces for the free circulation ofthe liquid which leads to strong losses of charges inside the reactor.

[0042] In FIG. 6, we see the aspect of the surface of the catalytic bedafter loading of the same catalyst as that used for the two previousloadings, but now carried out using the process as set forth in theinvention, meaning in a liquid. The grains are distributed in ahomogenous manner and on the whole even spaces are distributed aroundthe grains. Therefore, on the whole the molecules that make up thereaction liquid have the same probability of meeting the same quantityof catalyst grains, without being deviated by the presence of preferredpaths. This results in an even and sufficient flow, made easier by apresence that is also homogenous of spaces evenly distributed around thegrains, making it possible to optimize the desired chemical reaction.The loading is homogenous and dense.

[0043] The examples provided below are intended to illustrate theinvention and not limit it in any way.

EXAMPLE 1

[0044] Three series of tests were carried out in a laboratory using thesame catalyst, over a transparent column, whose dimensions are asfollow:

[0045] diameter 440 mm,

[0046] height 1000 mm.

[0047] The catalyst used for the tests is comprised mainly of aluminaand presents itself in the form of dry extrudates whose averagedimensions are as follows:

[0048] length: 5 mm,

[0049] diameter: 3 mm.

[0050] Test 1

[0051] The catalyst is loaded in the traditional way, meaning in agaseous phase (air), using a sleeve comprised of a flexible tube with adiameter of 10 cm.

[0052] Test 2

[0053] The same batch of catalyst is loaded in the air using thedistribution device with a Densicat type rain effect (dense loading),meaning including flexible rubber deflectors, integral with severallevels of an axis animated by a variable speed rotation movement.

[0054] Test 3

[0055] Prior to loading, we added a volume of water whose height is 100mm in the column.

[0056] The same batch of catalyst is loaded into this liquid with adistribution device that is identical to the one used in Test 2, meaningfavoring a dense load, as set forth in the invention.

[0057] The results obtained are summarized in Table 1 below. TABLE 1Test 1 Test 2 Test 3 Loading Method Sleeve Dense Loading Liquid Loadingmedium Air Air Water Height of Water 0 0 100 mm Quantity of loadedcatalyst 46.39 kg 46.39 kg 46.39 kg Density of the catalytic bed 0.780.90 0.77 (t/m³) State of the catalytic bed See FIG. 4 See FIG. 5 SeeFIG. 6

[0058] We see that the density of the catalytic mass obtained, with adense type loading method in air (Test 2), is greater on the whole by15% than that obtained by loading with a sleeve in air (Test 1).

[0059] Loading in a liquid (Test 3), carried out using the same deviceas that used for the dense loading (Test 2), but in a liquid, as setforth in the invention, makes it possible to significantly reduce thedensity whose value is considerably closer to the value recorded with asleeve loading. Therefore, when using the process as set forth in theinvention, we obtain a dense type loading in which the presence of theliquid makes it possible to significantly reduce the increase in densityof the catalytic mass inherent to this type of loading.

[0060] When checking FIGS. 4, 5 and 6, which are representations ofphotos of the surface of the catalytic bed obtained in each of the aboveloading tests, we see that the loading process as set forth in theinvention, while reducing the density of the catalytic mass to a valueclose to that obtained with the sleeve, it is also possible to obtain amostly homogenous distribution of the grains, as only the dense typeloadings in air can do currently, which, in counterpart, led to asignificant increase in the density of the load.

[0061] Therefore, the process as set forth in the invention provides asolution to the problem caused when obtaining a homogenous distributionthat usually results from a dense type loading, but whose density of theloaded mass here is for the most part identical to the density recordedwith a sleeve type distribution.

EXAMPLE 2

[0062] The above-mentioned tests are done over, but, in Test 3, theliquid has been replaced with an aqueous ethylene-glycol solution with aviscosity that is 17 to 18 times higher than that of water, to study theinfluence of the viscosity of the liquid being used.

[0063] The results obtained are shown in Table 2 below. TABLE 2 1 2 3Method of loading Sleeve Dense loading Liquid Loading medium Air AirWater + ethylene-glycol Height of the liquid 0 0 100 mm Quantity ofloaded catalyst 45.27 kg 45.27 kg 45.27 kg Density of the catalytic bed0.78 0.90 0.79 (t/m³)

[0064] We see that a greater liquid viscosity has no effect on theresults obtained and that the process as set forth in the invention doesnot depend on the viscosity of the liquid used for loading the catalystgrains.

1. Process for the homogenous loading of solid particles into a chamber(I), characterized in that said chamber (1) is filled at least in partwith a liquid (2), and in that the flow of particles (3) introduced intothe chamber (1) is divided, then dispersed in a homogenous manner in agaseous phase (4) over the surface (5) of the liquid, within which theparticles move downward by means of gravity to settle and form a fixedbed.
 2. Process as set forth in claim 1, characterized in that theliquid phase (2) is comprised of a liquid or a mixture of liquidsphysically and chemically compatible with the chemical nature of thesolid particles.
 3. Process as set forth in any one of claims 1 through2, characterized in that, throughout the loading, the height of theliquid (2) through which the solid particles pass, over the bed ofparticles being created, is greater than 10 cm.
 4. Process as set forthin any one of claims 1 through 3, characterized in that the gaseousphase is comprised of a gas or a mixture of gases physically andchemically compatible with the chemical nature of the solid particles.5. Process as set forth in any one of claims 1 through 4, characterizedin that the flow of particles (3) introduced into the chamber (1) isdivided, then distributed in a homogenous manner, using a device (4)that makes possible a rainlike distribution of said particles over theentire transversal section of the chamber (1).
 6. Process as set forthin claim 5, characterized in that the distribution device (4) iscomprised of flexible deflectors integral with several levels of an axisanimated with a rotary movement.
 7. Process as set forth in claims 5 and6, characterized in that the deflectors are articulated on the mobileaxis so as to be able to move upward under the effect of the centrifugalforce.
 8. Process as set forth in any one of claims 5 through 7,characterized in that the rotation speed of the mobile axis is less than200 rotations per minute and preferably less than 150 rotations perminute.
 9. Process as set forth in any one of claims 5 through 8,characterized in that each of the deflectors is comprised of a flexiblestrap.
 10. Process as set forth in any one of claims 5 through 8,characterized in that the particle distribution device is comprised of arigid matter.
 11. Process as set forth in any one of claims 1 through10, characterized in that the liquid phase (2) is the reaction liquid ofa chemical reactor.
 12. Process as set forth in any one of claims 1through 11, characterized in that the liquid phase (2) is a hydrocarbon,an aqueous phase, an alcohol or their derivatives.
 13. Process as setforth in any one of claims 1 through 12, characterized in that thegaseous phase is air.
 14. Process as set forth in any one of claims 1through 12, characterized in that the gaseous phase is a neutral orinert gas.
 15. Process as set forth in claim 14, characterized in thatthe neutral or inert gas is argon or nitrogen.
 16. Process as set forthin any one of claims 1 through 15, characterized in that the gas used isdried or dehydrated.
 17. Process as set forth in claims 1 through 17,characterized in that the solid particles have dimensions that rangebetween a few tenths of a millimeter and a few centimeters.
 18. Processas set forth in claim 17, characterized in that the solid particles aresaturated with a liquid prior to being loaded.
 19. Process as set forthin claims 1 through 18, characterized in that the chamber (1) is achemical reactor, whereas the particles (3) are grains of catalyst.